Abstract
A lipidomic and metabolomic investigation of serum and liver from mice was performed to gain insight into the tumor suppressor gene Hint1. A major reprogramming of lipid homeostasis was found in both serum and liver of Hint1-null (Hint(-/-)) mice, with significant changes in the levels of many lipid molecules, as compared with gender-, age-, and strain-matched WT mice. In the Hint1(-/-) mice, serum total and esterified cholesterol were reduced 2.5-fold, and lysophosphatidylcholines (LPCs) and lysophosphatidic acids were 10-fold elevated in serum, with a corresponding fall in phosphatidylcholines (PCs). In the liver, MUFAs and PUFAs, including arachidonic acid (AA) and its metabolic precursors, were also raised, as was mRNA encoding enzymes involved in AA de novo synthesis. There was also a significant 50% increase in hepatic macrophages in the Hint1(-/-) mice. Several hepatic ceramides and acylcarnitines were decreased in the livers of Hint1(-/-) mice. The changes in serum LPCs and PCs were neither related to hepatic phospholipase A2 activity nor to mRNAs encoding lysophosphatidylcholine acetyltransferases 1-4. The lipidomic phenotype of the Hint1(-/-) mouse revealed decreased inflammatory eicosanoids with elevated proliferative mediators that, combined with decreased ceramide apoptosis signaling molecules, may contribute to the tumor suppressor activity of Hint1.